The effects of going hungry in childhood may be more lasting than previously thought. Researchers studying people raised on Barbados who suffered severe starvation as infants found these adults were more anxious, less sociable, less interested in new experiences and more hostile than those who were well-nourished throughout childhood, according to a study published in the Journal of Child Psychology and Psychiatry.

Scientists led by Dr. Janina Galler of Harvard Medical School studied 77 children, born between 1967 and 1972, who were hospitalized for severe starvation syndromes known as marasmus or kwashiorkor at an average age of seven months, to determine how the malnutrition affected personality development.

Kwashiorkor results from a lack of protein and is marked by the protruding belly that has become a familiar symptom of child starvation. Marasmus is caused by poor caloric intake and children with this condition look more emaciated. Some children in the study had symptoms of both. Worldwide, nearly 3 million children under five die of hunger annually— and around 25% of the world’s children suffer stunted growth due to malnutrition, according to the World Health Organization.

The children in the study were enrolled in a hunger treatment and prevention program at the Barbados Nutrition Center, which provided food as well as home visits to monitor their recovery and nutrition education until they were 12. None of them had been born underweight or suffered from further starvation after the program started. Although their growth was stunted, they caught up with normal growth curves by adolescence. This group was compared with 57 school classmates, matched in age and gender, who had not suffered starvation.

The malnourished children were five times more likely to score higher than normal on tests of neuroticism — a trait that measures negative emotions and a tendency to feel uncontrollable distress— when they were in their 40s, compared to the well-nourished controls. Hunger also seemed to have an effect on suppressing development of extraversion, or sociability, since the children who had been starved were three times more likely to have abnormally low scores for this trait in middle age than the controls. The same was true with regard to conscientiousness, or the ability to reliably organize and follow through on plans.

Those who were malnourished during infancy were also more than 5 times as likely to have abnormally low scores on “openness to experience,” a measure of intellectual curiosity and independence. Although the differences were less pronounced, the malnourished group also showed reduced “agreeableness,” which rates whether people are hostile or altruistic.

“Poor nutrition early in life seems to predispose individuals to a suspicious personality, which may then fuel a hostile attitude toward others,” Adrian Raine, professor of psychology at the University of Pennsylvania, toldScience News, commenting on the research. Raine, who was not associated with the study, conducted earlier investigations of malnutrition and personality, which found that early life enrichment significantly mitigated some of the most extreme negative effects on personality.

In that research, Raine and his colleagues studied nearly 1,800 children from Mauritius, a tropical island off the coast of Madagascar. They found that if those who suffered malnutrition before age three were enrolled in a preschool nutrition, education and exercise program, they were 53% less likely to have conduct disorder at age 17 and 63% less likely to have been involved in crime at age 23, compared to malnourished controls who did not attend the program.

The new research suggests that more subtle effects on personality — short of outright clinical disorders or criminal behavior — may unfortunately persist despite enrichment. However, the children in the Barbados study were far more severely malnourished than those in Mauritius, so it’s possible that milder cases may be more amenable to intervention.

The authors conclude, “[A] single episode of malnutrition during the first year of life and associated conditions can have a long-term impact on personality… [A]t the individual case level, the malnourished participants were more likely to be classified outside the average range of personality scores.”

They suggest several ways that malnutrition might cause such lasting changes on personality. “One possibility is that early childhood malnutrition affects personality development via direct impacts on the brain,” they write. The brain is the most energy-hungry organ in the body, particularly in babies, so it may be most vulnerable to direct damage when nutrients and calories aren’t there.

Starvation could also cause depression in the children’s mothers, which may in turn have negative effects on children’s development and behavior. Research on children with profoundly depressed caregivers shows that when the mother is less responsive to the infants’ signals, the children can become more anxious, depressed and less able to manage distress. Even a father’s distress can affect unborn children in negative ways.

It’s also possible that starvation affects the expression of genes in the brain, perhaps steering the child toward a personality better adapted to a world of scarcity. In a world where food is hard to get, for example, being more anxious, suspicious and sensitive to threats may aid survival. Those same traits may be less helpful where resources are plentiful.

Regardless of how hunger is influencing personality changes, the results stress that starvation may lead to physiological changes with lasting psychological consequences: another reason, even if more aren’t needed, to improve efforts to fight childhood hunger.